The field of the present invention is related to a class of transportation machines commonly referred to as “walking machines,” which are large, typically non-wheeled power-driven structures operable for transporting massive and heavy loads, upwards of several thousand tons, over a road or other ground surface such as ground, snow, a prepared gravel area, etc. These machines, and the heavy substructures in themselves, are fabricated from steel and other high-strength materials and find particular use in carrying and sequentially transporting large and huge structures such as oil drilling rigs to position, and reposition them, over a drilling well bore in a new field undergoing exploration for oil, or over existing well bores in an old field previously worked, as needed.
Instead of using ground-contacting wheels to move the heavy loads, these walking machines typically comprise a plurality of lifting assemblies that usually use hydraulic lift cylinders to lift the load above the supporting surface and then move the load relative to the supporting surface by transporting the load via rollers or tracks in the walking machines.
In order to position the oil rig or other heavy load in a precise position, these walking machines may be provided with a steering mechanism whereby the walking machine unit may be rotated or steered to a desired position. U.S. Pat. No. 6,581,525, hereby incorporated by reference, shows walking machine systems and methods for moving heavy loads, such as oil rig structures. The U.S. Pat. No. 6,581,525 patent also discloses a steering system for a walking machine in which a substructure of the walking unit may be disengaged and rotated relative to its upper structure thus repositioning the substructure for travel at a desired steered angle. Other steering systems for walking machines are disclosed in U.S. Pat. Nos. 8,573,334 and 7,806,207. The present inventors have recognized that these steering systems have various limitations and potentially undesirable characteristics, which, depending upon the design, may include: only manual repositioning; complicated rotational position detection and control; complicated or unreliable rotational drive mechanisms; excessively high ground pressures and/or limitations on stroke.